This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A287438 #11 Nov 11 2024 18:10:02
%S A287438 0,1,2,1,2,0,2,1,0,1,2,0,2,1,0,0,1,2,2,1,0,1,2,0,0,1,2,1,2,0,2,1,0,0,
%T A287438 1,2,2,1,0,1,2,0,0,1,2,0,1,2,1,2,0,2,1,0,2,1,0,1,2,0,0,1,2,1,2,0,2,1,
%U A287438 0,0,1,2,0,1,2,1,2,0,2,1,0,1,2,0,2,1
%N A287438 Start with 0 and repeatedly substitute 0->012, 1->120, 2->210.
%C A287438 This is the fixed point of the morphism 0->012, 1->120, 2->201 starting with 0. Let u be the (nonperiodic) sequence of positions of 0, and likewise, v for 1 and w for 2; then u(n)/n -> 3, v(n)/n -> 3, w(n)/n -> 3.
%C A287438 See A287385 for a guide to related sequences.
%H A287438 Clark Kimberling, <a href="/A287438/b287438.txt">Table of n, a(n) for n = 1..10000</a>
%H A287438 <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>
%e A287438 First three iterations of the morphism: 012, 012120210, 012120210120210012210120012.
%t A287438 s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{1, 2, 0}, 2->{2, 1, 0}}] &, {0}, 9]; (*A287438*)
%t A287438 Flatten[Position[s, 0]]; (*A189728*)
%t A287438 Flatten[Position[s, 1]]; (*A189670*)
%t A287438 Flatten[Position[s, 2]]; (*A287441*)
%t A287438 SubstitutionSystem[{0->{0,1,2},1->{1,2,0},2->{2,1,0}},0,{5}][[1]] (* _Harvey P. Dale_, Nov 11 2024 *)
%Y A287438 Cf. A189728, A189670, A287385, A287441.
%K A287438 nonn,easy
%O A287438 1,3
%A A287438 _Clark Kimberling_, May 26 2017